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00045 #include "dsp.h"
00046 #include "preprocessor.h"
00047
00048 #if defined(FORCE_ALL_GENERICS) || \
00049 defined(FORCE_GENERIC_OP32_LN) || \
00050 !defined(TARGET_SPECIFIC_OP32_LN)
00051
00052 S64 dsp32_op_ln_raw(dsp32_t num)
00053 {
00054 dsp32_t num_temp;
00055 S64 a, a_sqr, res;
00056 int under_bit_val;
00057
00058
00059 if (num <= DSP32_Q(0.))
00060 return DSP_Q_MIN(DSP32_QA, DSP32_QB);
00061
00062
00063
00064 if (num > DSP32_Q(1.))
00065 {
00066 under_bit_val = 0;
00067 num_temp = num;
00068 while (num_temp > DSP32_Q(1.))
00069 {
00070 num_temp >>= 1;
00071 under_bit_val++;
00072 }
00073 num_temp = (num >> under_bit_val);
00074 }
00075 else
00076 {
00077 under_bit_val = 0;
00078 num_temp = num;
00079 while (num_temp < DSP32_Q(0.5))
00080 {
00081 num_temp <<= 1;
00082 under_bit_val++;
00083 }
00084 num_temp = (num << under_bit_val);
00085 }
00086
00087
00088 a = (((S64) num_temp) - DSP32_Q(1.)) << DSP32_QB;
00089 a = a/(((S64) num_temp) + DSP32_Q(1.));
00090
00091 a_sqr = (a*a) >> DSP32_QB;
00092
00093 res = (a_sqr*DSP32_Q(1./13.)) >> DSP32_QB;
00094 res = (a_sqr*(res + DSP32_Q(1./11.))) >> DSP32_QB;
00095 res = (a_sqr*(res + DSP32_Q(1./9.))) >> DSP32_QB;
00096 res = (a_sqr*(res + DSP32_Q(1./7.))) >> DSP32_QB;
00097 res = (a_sqr*(res + DSP32_Q(1./5.))) >> DSP32_QB;
00098 res = (a_sqr*(res + DSP32_Q(1./3.))) >> DSP32_QB;
00099 res = (a*(res + DSP32_Q(1.))) >> (DSP32_QB - 1);
00100
00101 if (num > DSP32_Q(1.))
00102 res += ((S64) under_bit_val)*((S64) DSP32_Q(CST_LN_2));
00103 else
00104 res -= ((S64) under_bit_val)*((S64) DSP32_Q(CST_LN_2));
00105
00106 return res;
00107 }
00108
00109 #endif